Biomedical engineering company Össur has announced the successful development of a thought controlled bionic prosthetic leg. The new technology uses implanted sensors sending wireless signals to the artificial limb's built-in computer, enabling subconscious, real-time control and faster, more natural responses and movements.

Prosthetics controlled by muscle impulses have been around since the late 1960s, but the technology has severe limitations. It works by laying sensors on the skin of the vestigial limb, which picks up electrical impulses that control, for example, an artificial arm. The trouble is, these sensors pick up electric impulses from more than one muscle. This degrades performance, requires a lot of practice to operate properly, and makes the prosthesis slow, Imprecise, and frustrating to use.

One answer to this is to use more precise sensor arrangements that make the limb, for all practical purposes, mind-controlled. The method is already used with great success on upper limbs and even artificial hands, but, paradoxically, it's been less successful with lower limbs.

The problem is that upper limbs use more conscious control than the lower ones. We use arms and hands for actually doing things like picking up a cup or working a screwdriver so we do a lot of the heavy work of coordination. By contrast, we use legs for getting around and our control is much less conscious. Essentially, the legs need to control themselves by means of reflexes triggered by the spinal cord rather than direct commands from the brain.

For example, we can put on a pair of socks without being aware of what a complex series of movements we execute with the foot and ankle without any awareness. The leg and foot just do what they’re supposed to do. But without this automatic adjustment by our neuromuscular system, clearing a doorstep without stumbling becomes a major accomplishment.

Össur's new mind-controlled technology for lower-limb prosthetics is designed to be compatible with its line of bionic feet, knees, and legs. These bionic prostheses are computerized smart limbs capable of real-time learning with the ability to adjust themselves to the wearer's gait as well as the walking speed and terrain.

The control system works by means of Implanted MyoElectric Sensors (IMES) developed by the Alfred Mann Foundation. The size of a matchstick, these are implanted into specific remnant muscles in the limb stump. Meanwhile, a coiled-wire receiver inside the prosthesis' cup picks up the impulses and transmits them wirelessly to the robotic limb's computer. Together, the IMES and robotic limb act as a sort cybernetic spinal cord. Instead of the wearer consciously controlling the limb's movements, the wearer sends an unconscious command to the prosthesis, which controls the movement.

"The technology allows the user’s experience with their prosthesis to become more intuitive and integrative," says Thorvaldur Ingvarsson, leader of the mind-controlled prosthetics project. "The result is the instantaneous physical movement of the prosthesis however the amputee intended. They no longer need to think about their movements because their unconscious reflexes are automatically converted into myoelectric impulses that control their Bionic prosthesis."

Two volunteers have had the technology implanted for a year as part of the First-in-Man research project. Both participating amputees were positive about the new technology and clinical trials are continuing.

The announcement was made today by Jon Sigurdsson, President & CEO of Össur, the global innovator credited with creating the world’s first Bionic prostheses for amputees.

"Mind-controlled Bionic prosthetic legs are a remarkable clinical breakthrough in next-generation Bionic technology," said Jon Sigurdsson, President & CEO of Össur. "By adapting not only to the individual’s intentional movements but to intuitive actions, we are closer than ever to creating prosthetics that are truly integrated with their user."